Sorption and bioavailability of phosphorus during the drainage period of flooded-drained soils

Summary Changes in P sorption and bioavailability were studied with 4 soils previously flooded and drained as occurs in rice-based cropping systems. Phosphorus sorption was measured at 15 and 119 days after drainage and the bioavailability of added and native soil-P was determined at 9, 16, 30, 45, 70 and 135 days in both flooded-drained and unflooded soils. The P sorptivity and bonding energy of sorption increased under flooded-drained soil conditions. At 119 days after drainage the P sorptivity and bonding energy of sorption decreased as compared to 15 days after drainage. The P sorptivity of the flooded-drained soils, however, did not reach the same levels as existed in the soils prior to flooding. The bioavailability of P during the drainage period remained low and did not measurably change up to 70 days after drainage. At 135 days after drainage the bioavailability of P increased significantly, but did not reach the level found in the corresponding unflooded soils.     

温度和水分对草甸草原土壤氧化亚氮产生速率的调控

通过试验室模拟试验,研究了调控草甸草原黑钙土N₂O产生速率的因素.结果表明,土壤水分对草甸草原土壤N₂O产生速率有重要影响(F=6.149,P＜0.01).但相关性分析表明,草甸草原土壤含水量与N₂O的产生速率间线性相关不显著.就土壤N₂O的产生速率而言,温度的影响远低于土壤水分的影响(F=2.275,P=0.106).土壤水分和温度对不同生长阶段的草甸草原土壤N₂O产生速率的调控作用主要表现为阶段性的多阶多项式关系：y=ax³+bx²+cx+d,其中a、b、c、d是常数.     

Esterification reactions catalyzed by lipases immobilized in organogels: effect of temperature and substrate diffusion

Rhizomucor miehei lipase was immobilized in hydroxy(propylmethyl) cellulose or agar gels containing lecithin or AOT microemulsions. The effect of the diffusion of substrates and products to this catalyst was studied, as well as the effect of temperature on the initial rate of ester synthesis. The composition of the gel affects the reaction rate due to mass transport phenomena. The apparent activation energies were higher for the systems based on agar, independently of the microemulsion used, and lower for the systems based on AOT microemulsions, independently of the polymer used.     

不同施磷量对春油菜产量和土壤磷素平衡的影响

青海省东部春油菜主产区的土壤速效磷含量高、磷肥施用量大、磷肥利用率低。研究不同施磷量对春油菜的生长、磷素吸收和利用、土壤磷素平衡的影响,可为该地区春油菜田养分高效管理提供科学依据,对保障青藏高原农业可持续发展具有重要意义。本研究于2017和2018年在青海省互助县开展了田间试验,设置0、30、60、90、120 kg P₂O₅·hm^-2 5个磷肥施用量,测定了不同处理春油菜的产量、磷素吸收与利用、籽粒含油率等。结果表明: 2017年施磷量60 kg·hm^-2处理的油菜籽粒产量、成熟期地上部磷素累积量和产油量均显著高于不施磷处理,但施磷量超过60 kg·hm^-2后,籽粒产量和产油量不再增加;2018年施磷量对春油菜籽粒产量、成熟期地上部磷素累积量和产油量均无显著影响。两年度的磷肥表观利用率均很低,平均为6.7%。施用磷肥条件下土壤均有不同程度的磷素盈余,施磷量低于60 kg·hm^-2时盈余量较低。综合考虑春油菜产量、产油量、磷肥表观利用率和土壤磷素表观平衡,在青海省东部春油菜区,推荐施磷量为60 kg·hm^-2。     

The influence of temperature on the flocculation rate of renneted casein micelles

The flocculation rate constant of completely renneted casein micelles in milk ultrafiltrate was measured by Rayleigh light scattering between 20 and 35 degrees C. In this temperature range an apparent energy of activation of 103 kJ mol (+/-11 kJ mol : n = 50) was measured. At 15 degrees C clotting was not longer perceptible. The activation of the flocculation between 20 and 35 degrees C is explained not so much by the height of the energy barrier separating the clotting micelles, as by the very negative temperature coefficient of that barrier. In line with this conclusion it is suggested that renneted micelles adhere through hydrophobic bonding. The flocculation rate constant of renneted casein micelles is independent of micelle size at the four temperature levels studied.     

秸秆覆盖与施磷对四川丘陵旱地土壤磷形态及有效性的影响

为揭示秸秆覆盖配施磷肥下土壤无机磷形态变化规律及磷的有效性,本研究采用二因素裂区设计,主区为秸秆覆盖和不覆盖,副区为3个施磷量(0、75和120 kg·hm^-2),分析秸秆覆盖与施磷条件下四川丘陵旱地紫色土磷吸附-解吸特征、无机磷组分含量及其与有效磷的关系。结果表明: 2018—2020年两个试验年度秸秆覆盖处理比不覆盖处理土壤磷最大吸附量分别显著降低7.7%和7.4%,磷吸附饱和度分别显著增加35.4%和18.6%,土壤易解吸磷分别显著提高21.6%和35.2%,磷最大缓冲容量无显著差异;施磷与不施磷相比,磷最大吸附量和最大缓冲容量显著降低,吸附饱和度显著增加,易解吸磷则随施磷量的增加而增加。两个试验年度秸秆覆盖处理比不覆盖处理磷酸二钙(Ca₂-P)、磷酸八钙(Ca₈-P)和铁磷(Fe-P)含量显著增加,铝磷(Al-P)含量显著降低,闭蓄态磷(O-P)和磷灰石(Ca₁₀-P)含量有降低的趋势;与不施磷相比,施磷则提高了不同无机磷组分含量。与不覆盖处理相比,两个试验年度秸秆覆盖处理土壤有效磷含量分别显著增加23.2%和9.6%,磷活化系数分别显著提高21.3%和8.9%,且土壤有效磷含量和磷活化系数均随施磷量的增加而提高。回归分析表明,无机磷各组分对紫色土有效磷有效性的贡献为Ca₂-P>Fe-P>Al-P>Ca₈-P>Ca₁₀-P>O-P。因此,秸秆覆盖配施磷肥促进了土壤难溶性磷向中等活性或易于作物吸收的磷形态分解和转化,降低土壤对磷素的吸附,促进土壤磷素的解吸,最终提高土壤磷素有效性。综合考虑经济效益,推荐四川丘陵旱地秸秆覆盖配施75 kg·hm^-2磷肥更有利于提高土壤磷素有效性。     

Leaf nonstructural carbohydrate concentrations of understory woody species regulated by soil phosphorus availability in a tropical forest

Leaf soluble sugars and starch are important components of nonstructural carbohydrates (NSCs), which are crucial for plant growth, development, and reproduction. Although there is a large body of research focusing on the regulation of plant NSC (soluble sugars and starch) concentrations, the response of foliar NSC concentrations to continuous nitrogen (N) and phosphorus (P) addition is still unclear, especially in tropical forests. Here, we used a long‐term manipulative field experiment to investigate the response of leaf NSC concentrations to continuous N and P addition (3‐, 5‐, and 8‐year fertilization) in a tropical forest in southern China. We found significant species‐specific variation in leaf NSC concentrations in this tropical forest. Phosphorus addition dramatically decreased both leaf soluble sugar and starch concentrations, while N addition had no significant effects on leaf soluble sugar and starch concentrations. These results suggest that, in plants growing in P‐limiting tropical soil, leaf NSC concentrations are regulated by soil P availability rather than N availability. Moreover, the negative relationships between NSC concentrations and leaf mass per area (LMA) revealed that NSCs could supply excess carbon (C) for leaf expansion under P addition. This was further supported by the increased structural P fraction after P fertilization in our previous study at the same site. We conclude that soil P availability strongly regulates leaf starch and soluble sugar concentrations in the tropical tree species included in this study. The response of leaf NSC concentrations to long‐term N and P addition can reflect the close relationships between plant C dynamics and soil nutrient availability in tropical forests. Maintaining relatively higher leaf NSC concentrations in tropical plants can be a potential mechanism for adapting to P‐deficient conditions.     

Effects of short-term soil flooding on stomata behaviour and leaf gas exchange in barley plants

Exposure of barley plants (Hordeum vulgare L.) to soil flooding for 2 to 24 h reduced the net photosynthetic rate and transpiration rate. Stomatal conductance also decreased in flooded plants. Stomatal closure started within 2 – 6 h and stomata remained closed up to 24 h of treatment.     

Effects of rapid temperature fluctuations prior to breeding on reproductive efficiency in replacement gilts

Rapidly cooling pigs after heat stress (HS) results in a pathophysiological condition, and because rapid temperature fluctuations may be associated with reduced reproductive success in sows, it lends itself to the hypothesis that these conditions may be linked. Objectives were to determine the effects of rapid cooling on thermal response and future reproductive success in pigs. Thirty-six replacement gilts (137.8±0.9 kg BW) were estrus synchronized and then 14.1±0.4 d after estrus confirmation, pigs were exposed to thermoneutral conditions (TN; n=12; 19.7±0.9°C) for 6 h, or HS (36.3±0.5°C) for 3 h, followed by 3 h of rapid cooling (HSRC; n=12; immediate TN exposure and water dousing) or gradual cooling (HSGC; n=12; gradual decrease to TN conditions) repeated over 2 d. Vaginal (T_V) and gastrointestinal tract temperatures (T_GI) were obtained every 15 min, and blood was collected on d 1 and d 2 during the HS and recovery periods at 180 and 60 min, respectively. Pigs were bred 8.3±0.8 d after thermal treatments over 2 d. Reproductive tracts were collected and total fetus number and viability were recorded 28.0±0.8 d after insemination. HS increased T_V and T_GI (P=0.01; 0.98 °C) in HSRC and HSGC compared to TN pigs. During recovery, T_V was reduced from 15 to 105 min (P=0.01; 0.33 °C) in HSRC compared to HSGC pigs, but no overall differences in T_GI were detected (P<0.05; 39.67 °C). Rapid cooling increased (P<0.05) TNFα compared to HSGC and TN pigs during recovery-d 1 (55.2%), HS-d 2 (35.1%), and recovery-d 2 (64.9%). Viable fetuses tended to be reduced (P=0.08; 10.5%) and moribund fetuses tended to be increased (P=0.09; 159.3%) in HSRC compared to HSGC and TN pigs. In summary, rapid cooling prior to breeding may contribute to reduced fetal viability and reproductive success in pigs.     

Effects of soil phosphorus availability,temperature and moisture on soil respiration in Eucalyptus pauciflora forest

Rates of soil respiration (CO₂ efflux) were measured for a year in a mature Eucalyptus pauciflora forest in unfertilized and phosphorus-fertilized plots. Soil CO₂ efflux showed a distinct seasonal trend, and average daily rates ranged from 124 to 574 mg CO₂ m^–2 hr^–1. Temperature and moisture are the main variables that cause variation in soil CO₂ efflux; hence their effects were investigated over a year so as to then differentiate the treatment effect of phosphorus (P) nutrition.Soil temperature had the greatest effect on CO₂ efflux and exhibited a highly significant logarithmic relationship (r² = 0.81). Periods of low soil and litter moisture occurred during summer when temperatures were greater than 10 °C, and this resulted in depression of soil CO₂ efflux. During winter, when temperatures were less than 10 °C, soil and litter moisture were consistently high and thus their variation had little effect on soil CO₂ efflux. A multiple regression model including soil temperature, and soil and litter moisture accounted for 97% of the variance in rates of CO₂ efflux, and thus can be used to predict soil CO₂ efflux at this site with high accuracy. Total annual efflux of carbon from soil was estimated to be 7.11 t C ha^–1 yr^–1. The model was used to predict changes in this annual flux if temperature and moisture conditions were altered. The extent to which coefficients of the model differ among sites and forest types requires testing.Increased soil P availability resulted in a large increase in stem growth of trees but a reduction in the rate of soil CO₂ efflux by approximately 8%. This reduction is suggested to be due to lower root activity resulting from reduced allocation of assimilate belowground. Root activity changed when P was added to microsites within plots, and via the whole tree root system at the plot level. These relationships of belowground carbon fluxes with temperature, moisture and nutrient availability provide essential information for understanding and predicting potential changes in forest ecosystems in response to land use management or climate change.     

温度对橄榄蛏蚌耗氧和氨氮排泄的影响

The respiration metabolismand excretion of marinebivalves were studied by different researchers[1—6].Themetabolic rate of bivalves is influenced by a number ofvariables,includingtemperature,body size,oxygen ten-sion,food concentration,reproductive state,activityleveland physiological condition.The excreted metabolites ofbivalves include ammonia,urea,uric acid and others,with ammonia comprising70%of the total excretion.Solenaia oleivorais a proper freshwater bivalve in China.For the consumer it has the follo...     

土壤可溶性无机磷对微生物生物量磷测定的干扰

对于可溶性无机磷含量高于50mg/kg土的土壤,薰蒸处理前必须去除这部分磷,否则将严重干扰微生物量磷的测定,讨论了去除土壤中可溶性无机磷的方法。     

施磷量与施磷深度对玉米-大豆套作系统磷素利用率及磷流失风险的影响

为充分发挥间套作种植体系磷素高效利用优势、降低土壤磷素流失,采用田间试验分析了3种施磷(P_2O_5)水平(CP:168 kg·hm^-2;RP_1:135 kg·hm^-2;RP_2:101 kg·hm^-2)与3个施磷深度(D_1:集中施在距离地面5 cm处;D_2:集中施在距离地面15 cm处;D_3:于距离地面5、15 cm处各施一半)处理下玉米-大豆套作系统作物地上部生物量、籽粒产量、植株吸磷量、土壤全磷与速效磷含量、磷吸附-解吸特征,以期为优化西南玉米-大豆套作系统磷素管理提供理论依据.结果表明:与对照不施磷处理(P_0)相比,各施磷处理显著增加了作物地上部生物量、籽粒产量、植株吸磷量、土壤全磷和速效磷含量.相同施肥深度下,处理RP_1与CP相比,作物籽粒产量差异不显著,但显著提高了植株地上部吸磷量,因此RP_1处理的磷素表观利用率显著高于CP处理.相同施磷量下,不同施磷深度间比较,作物地上部生物量、籽粒产量、植株吸磷量、土壤全磷和速效磷含量均以D_2处理最高.依据土壤磷的吸附-解吸特征参数可知,当施磷深度为D_2、施磷量为RP_1时,土壤对磷的固持能力最强,在降低磷素流失上表现出较强优势.因此,玉米-大豆套作系统中适当减少磷肥施用量和加大磷肥施用深度在保证作物产量的同时,有利于提高磷素利用率,减少土壤磷流失.     

Study of the effects of temperature and pH on lactic acid production from fresh cassava roots in tofu liquid waste by Streptococcus bovis

We report a study of the effects of temperature and pH on the kinetics of lactic acid production from fresh cassava roots (FCR) by Streptococcus bovis in new media: tofu liquid waste (TLW); TLW with 2 wt% concentrated maguro waste (TLW + CMW2); and in a standard trypto-soya broth (TSB) compared with a standard medium (glucose in TSB). The results showed that 39 °C and pH 5.5 were optimal for fermentation properties (lactic acid concentration, productivity and specific growth rate) in all media, including the standard. The energy of activation (E_a) and the energy of deactivation (E_d) of lactic acid fermentation in all media were calculated using the Arrhenius relation. The E_a and E_d values increased in the order FCR in TLW < FCR in TLW + CMW2 < glucose in TSB < FCR in TSB, while values of productivity and specific growth rate decreased in the same order. The effects of pH on productivity and specific growth rate were evaluated by Michaelis–Menten and Monod-type equations. For pH, the inhibition is competitive for both productivity and specific growth rate. By controlling the pH at 5.80, the inhibition for both productivity and specific growth rate were minimized in all media.     

Effects of winter flooding on phosphorus dynamics in rice fields

Limnology - Controlling phosphorous (P) loads from rice fields is important for the conservation of aquatic ecosystems, in part because P is relatively concentrated at its sources. Recently, winter...     

Effect of temperature on nitrification intensity in soil

The temperature dependence of nitrification can be expressed by the Arrhenius equation while the time course of nitrate production can be expressed by the Gomperz function. These two findings served as a basis for a mathematical model which makes it possible to calculate nitrate production in the soil even when the temperature changes once or more times during the incubation.     

Effects of aerobic exercise and gender on visual and auditory P300, reaction time, and accuracy

Visual and auditory reaction times (RTs) have been reported to decrease during moderate aerobic exercise, and this has been interpreted as reflecting an exercise-induced activation (EIA) of cognitive information processing. In the present study we examined changes in several independent measures of information processing (RT, accuracy, P300 latency and amplitude) during exercise, and their relationship to visual or auditory modalities and to gender. P300 latencies offer independent measures of cognitive speed that are unrelated to motor output, and P300 amplitudes have been used as measures of attentional allocation. Twenty-four healthy college students [mean (SD) age 20 (2) years] performed auditory and visual "oddball" tasks during resting baseline, aerobic exercise, and recovery periods. Consistent with previous studies, both visual and auditory RTs during exercise were significantly shortened compared to control and recovery periods (which did not differ from each other). We now report that, paralleling the RT changes, auditory and visual P300 latencies decreased during exercise, indicating the occurrence of faster cognitive information processing in both sensory modalities. However, both auditory and visual P300 amplitudes decreased during exercise, suggesting diminished attentional resource allocation. In addition, error rates increased during exercise. Taken together, these results suggest that the enhancement of cognitive information processing speed during moderate aerobic exercise, although operating across genders and sensory modalities, is not a global facilitation of cognition, but is accompanied by decreased attention and increased errors.     

长期施磷对石灰性土壤中编码碱性磷酸酶基因的细菌群落的影响

[目的]通过研究集约化玉米体系中长期不同供磷水平对土壤中编码碱性磷酸酶基因的细菌群落多样性、结构、组成和网络特征的影响及其与土壤有机磷形态之间的关系,为探究有机磷循环功能在微生物的群落特征及提高土壤中有机磷矿化和利用提供科学依据.[方法]本研究依托华北平原小麦玉米轮作体系石灰性土壤长期施磷的定位试验(始于2008年),...     

养分和水添加对弃耕草地土壤无机磷组分的影响

合理的养分和水分管理措施是提高退化草地生产力和生物多样性的有效途径,但养分和水添加对弃耕草地土壤无机磷组分的影响研究较少.本文依托内蒙古多伦县2005年建立的养分(N∶ 10 g·m-2·a-1、P∶ 10g·m-2·a-1)和水分(植物生长季增水180 mm)添加田间试验,研究了表土(0～10 cm)无机磷组分及有效...     

温度和施磷对石灰性潮土小麦苗期生长及磷形态的影响

以石灰性潮土为对象,通过盆栽试验研究温度和磷肥对小麦苗期生长和土壤无机磷形态转化的影响.结果表明: 温度和磷肥是影响小麦生长的重要因子,但二者交互作用影响不显著.温度对小麦生长的影响大于施用磷肥,15 ℃是小麦苗期的适宜生长温度.与不施磷肥(-P)处理相比,5 ℃下,施磷肥(＋P)处理显著促进了小麦生长,小麦地上部、根部生物量分别提高18.2%、33.3%,地上部、根部磷素积累量分别提高30.6%、13.3%,根冠比、株高、分蘖、根系活力分别提高3.5%、10.0%、10.5%、70.3%;15 ℃下,施用磷肥对小麦生物量、分蘖影响不显著,但小麦地上部、根部磷素积累量分别提高32.3%、23.8%,根冠比、株高、根系活力分别提高15.6%、2.5%、32.8%;25 ℃下施用磷肥对小麦生长没有促进作用. 3种温度下,施磷能显著增加各处理土壤有效磷(Olsen-P)、二钙磷(Ca₂-P)、八钙磷(Ca₈-P)、铝磷(Al-P)和铁磷(Fe-P)含量.-P和+P处理下,温度对Ca₂-P含量影响不显著,对Olsen-P、Ca₈-P、Fe-P、Al-P含量影响显著.Ca₈-P、Fe-P含量表现为5 ℃>15 ℃>25 ℃;Al-P含量表现为25 ℃>15 ℃>5 ℃.小麦苗期可以吸收利用根际土壤Ca₂-P、Ca₈-P、Al-P、Fe-P,而Al-P、Fe-P对小麦的有效性明显低于Ca₂-P、Ca₈-P.各处理pH、闭蓄态磷(O-P)和十钙磷(Ca₁₀-P)差异不显著.总之,温度主要通过影响小麦生长来影响磷素吸收,低温下施用磷肥能显著促进小麦生长,高温能加速石灰性土壤有效磷的固定,施磷能缓解这一过程.